A survey of locations at a survey site may involve use of location coordinates from previously-surveyed locations, such as recognizable landmarks and other survey monuments, together with generation of location coordinates for newly-surveyed locations. Even where location coordinates for only newly-surveyed locations are used, these coordinates may not be fully consistent with each other when corrections are made for any errors introduced by use of a local coordinate system. The location coordinates of these locations, representing newly-surveyed locations and/or previously-surveyed locations, must be made consistent with each other in some "best fit" sense. Several workers have considered the problems of representation of locations on a map or chart display and/or adjustment of location coordinates.
Maps and charts have been prepared and used in connection with various location determination systems (LDSs), such as GPS, GLONASS, Loran, Tacan, Decca, Omega, VOR, DME, JTIDS, PLRS and an FM subcarrier system. Potter et al, in U.S. Pat. No. 3,659,085, disclose use of a computer for determining the location of objects in a chosen coordinate system. A mobile station in an aircraft, marine vessel or land vehicle, moving relative to the local landscape, transmits pulse signals to a large number of signal receiving stations, all linked to a central computer. Time of signal arrival, trilateralization, differential time of arrival or other techniques are used to solve for the present location of the mobile station, based on receipt of the transmitted signals and weighting of received signals to minimize some associated errors. Iterative computations are used to determine the optimum weighting.
In U.S. Pat. No. 4,135,190, DiMatteo et al disclose a navigational plotter system including a geographical map with location lines prepared with the aid of a Loran or Omega LDS. Intersections of location lines with coordinate baselines located on the map are recorded in coded form for direct readout of a selected location, for tracking of location and/or movement of a vehicle or vessel across the two-dimensional surface represented by the map.
A navigation display that provides a continuous pictorial or graphical display of the present location of a movable vehicle or vessel, using an LDS such as VOR, Loran, ADF, DME or Tacan, is disclosed by Scovill in U.S. Pat. No. 4,253,150. The charts are stored on photographic fllm, and the portion of the film displayed is varied to include the present location. This system can be used to provide readout of present ground speed of the vehicle or vessel, bearing, and estimated time to reach a waypoint or the destination. Most of the discussion is concerned with positioning of the portion of the film displayed.
In U.S. Pat. No. 4,428,052, Robinson et al disclose a navigational aid and autopilot system that includes display of a selected portion of a chart showing the location of a vehicle or vessel being tracked. The vehicle or vessel location may be shown at the center or near an edge of the portion of the chart displayed. Water and nearby land masses may be displayed on the selected portion of the chart, as well as relevant information such as the depth of the water at a location near a land mass.
Setliff et al disclose an electronic chart system that stores and visually displays a plurality of charts or maps digitally, where the charts have been prepared using a location determination system, such as Loran, in U.S. Pat. No. 4,428,057. The visually displayed image can be compressed or expanded to meet the current needs of the viewer. Each point on the chart is given an index, indicating whether that point is "land" or "water." Navigation information, such as location and bearing for a moving object, is available.
A navigation system, including an integrated electronic display for charts or maps prepared by a location determination system such as Loran or Decca, is disclosed in U.S. Pat. No. 4,590,569, issued to Rogoff et al. A plurality of charts is stored digitally and displayed as needed, together with alphanumeric data such as location coordinates, bearing, waypoints, and estimated time before arrival at a waypoint or destination. Radar return signals are received from nearby land masses, and this information is superimposed on the stored images in some situations. If the object tracked is located off-shore, the off-shore LDS receives (Loran) offset data from a plurality of on-shore LDS monitors to periodically correct the location of the off-shore object.
U.S. Pat. No. 4,685,068, issued to Greco et al, discloses a map digitization and feature extraction system that uses pattern recognition to add editable features, such as terrain elevation, vegetation, water storage and transport facilities, and electrical communication lines, to an electronic map that is being assembled. The added features are drawn from one or more separate databases, and features of the same class can be given the same color for display. A first visual display monitor for an interim or working display and a second monitor for final display, are preferably positioned adjacent to each other. A paper map, used for feature placement or details, is cut or sectioned into rectangles of length a few km on a side, and the sections are scanned into a computer for storage and subsequent use.
Green et al disclose a method for accurately displaying location information, obtained from a Loran system, on a map in U.S. Pat. No. 4,791,572. The actual locations of various Loran antenna monuments are determined and used together with Loran data to enhance the accuracy of a location on the map, by distorting map grid lines if necessary. Reconciliation of a location shown on two different maps is not provided.
A map-aided navigation system that uses TERCOM-SITAN control signals is disclosed by U.S. Pat. No. 4,829,304, issued to Baird. An aircraft flies over terrain to be mapped and estimates aircraft location and altitude at a sequence of sampling points. These data are Kalman filtered, and the resulting filtered data are used to determine elevation and slope for this terrain. On a subsequent flight over this terrain, an aircraft uses altimeter sensing and the terrain map to determine the most likely flight path actually followed by the aircraft.
A system for calibrating the locations of non-contact measurement sensors is disclosed in U.S. Pat. No. 4,841,460, issued to Dewar et al. A target is positioned within the measuring zone of one or more sensors and with the measuring zone of an external location determination system (LDS). Each sensor, together with the LDS, determines the location coordinates of the target within the reference frame of the measuring instrument, and transform matrices are used to relate these location coordinates in the different frames to a selected coordinate system. The sensors are calibrated by requiring that the different location coordinates for the target agree with each other, when expressed in the selected coordinate system.
Gray et al disclose a method for accurately updating location information contained in a digital map, in U.S. Pat. No. 4,891,761. A vehicle is dispatched to a neighborhood of an unknown location, which may be a landmark that has not yet been surveyed. The vehicle moves along a segment between a known landmark, such as an already-surveyed intersection and the unknown location and transmits location information to a central station to produce an updated digital map.
U.S. Pat. No. 4,899,161, issued to Morin et al, discloses a coordinate conversion system for air traffic control applications. Radar observable variables, such as target slant range, azimuth angle and altitude are transformed to a selected coordinate system centered at the target. The system converts from geodetic coordinates to ellipsoidal or conformal spherical coordinates, then to target location coordinates, followed by stereographic projection that preserves azimuthal angles for display of the target-aircraft spatial relationship. Elevation information is not available after stereographic projection is implemented.
A method for representing digitized image data for forming cross-sectional images of an object is disclosed by Essinger et al in U.S. Pat. No. 4,939,646. This method is useful in computer-assisted tomography, magnetic resonance imaging and other fields where three-dimensional representations are needed. A two-dimensional "slice" of a three-dimensional object is limited by a boundary curve, and image features within this curve are represented as locations in polar coordinates. A locus of points equidistant from and lying within the boundary curve is used for feature location and placement.
Another method of digitizing two-dimensional sections of a three-dimensional object is disclosed by Koch in U.S. Pat. No. 5,231,470.
In U.S. Pat. No. 4,939,661, issued to Barker et al, a marine navigation system that represents locations in cells that cumulatively cover an entire region is disclosed . Only those cells that contain a portion of a coastline have much associated location data.
A vehicle navigation system that uses local topographical maps to correct an aircraft flight path is disclosed in U.S. Pat. No. 4,939,663, issued to Baird. During flight, local altitude measurements are made and used with a digital database containing local elevation (above a ground reference surface) of the Earth's surface. The location of the aircraft is sampled separately and is compared with the local elevation contour corresponding to the altimeter measurement; a location correction is determined that places the aircraft location over the elevation contour. Here, the local altitude coordinate of the aircraft is determined exclusively by the altimeter measurement, and the other two aircraft position coordinates are determined approximately by independent position sampling, which may use aircraft dead reckoning.
Evans et al, in U.S. Pat. No. 4,954,833, disclose a method for converting GPS-determined location coordinates, expressed in a natural coordinate frame involving geodetic azimuth, to a coordinate system involving astronomical azimuth. In U.S. Pat. No. 5,030,957, Evans discloses a method for simultaneously measuring height in two coordinate systems, orthometric and geometric, using GPS receiver antennas attached to the top of survey leveling rods.
U.S. Pat. No. 4,982,332, issued to Saito et al, discloses a road data generating system is disclosed for use in an on-board vehicle navigation system. Locations of points on roads on a map are determined and stored, by reference of each such point to a nearest road intersection based on location data sensed by the moving vehicle. These data are compared with any extant location data for that road, and extant data are replaced on the map by new data at a given location that are believed to be more accurate than the extant data near that location.
A method for compensating for errors in determination of location coordinates of a plurality of selected locations is disclosed by Soderberg et al in U.S. Pat. No. 4,982,504. One or more reference locations, whose coordinates are assumed to be known with high accuracy, are introduced. A location determination probe or tool is moved to one of these reference locations and location measurements are taken at location near to but displaced from the reference location(s) and compared with computed location coordinates for these locations displaced from the reference location. Errors found in these comparisons are used, in a manner not filly discussed by the inventor, to correct the measured location coordinates for other locations.
Dedieu et al, in U.S. Pat. No. 4,998,212, disclose a method of representing a geographical map as an assembly of curvilinear trapezoids that fit together along their common edges, in a manner that approximates sections that occur on a globe surface of the Earth. The map sections are deformed and rotated and fitted together to provide a representation of a region of interest.
In U.S. Pat. No. 5,001,647, Rapiejko et al disclose an inertial transformation matrix generator that generates a sequence of successive incremental Euler transformation matrices to follow the motion of a moving aircraft. Rate-sensing gyros, mounted on the housing of the craft, independently sense the motion of the craft in three mutually orthogonal directions. The present spatial orientation of the craft is periodically corrected by independent measurements made by an inertial navigation system mounted on the craft.
A map and text display system for aircraft navigation is disclosed by Factor et al in U.S. Pat. No. 5,057,835. The system stores terrain elevation information for regions adjacent to a flight path and compares the presently measured aircraft altitude with the maximum terrain elevation for the local region over which the aircraft is positioned, to determine if the aircraft altitude is above a safety threshold for that region. Aircraft latitude, longitude and altitude are determined conventionally, and no second source of aircraft altitude information is used to vary or improve the altitude estimate.
Moroto et al disclose a display system for a user of land vehicle or aircraft navigation apparatus, in U.S. Pat. No. 5,121,326. An on-board database contains map data for the local terrain, including roads, road intersections and selected landmarks, in a chosen location coordinate system. These map data are transformed to a display coordinate system that moves with the user and is visibly displayed on a screen for the user. The transformations include rotations and translations of the stored map data.
U.S. Pat. No. 5,128,684, issued to Brown, discloses use of a system of spaced apart sensors for correlating detected sensor events in space and time. These sensors may, for example, detect radar signals or echoes to determine target tracks of a radar target. Present angular locations and rates of change of angle, as sensed at each sensor, are correlated with each other using a trigonometric scoring function and assigning the moving target location to one of a plurality of fixed spatial bins with selected volumes.
A system for perspective display of part of a topographic map for a moving vehicle is disclosed in U.S. Pat. No. 5,161,886, issued to De Jong et al. The system uses coordinate transformations that create and display the region surrounding the present location of the vehicle on a chosen local surface, which moves with the vehicle. The direction of motion of the vehicle determines the orientation of the displayed portion of the map.
Currin et al disclose a method for forming a composite terrain map from a mosaic of component images in U.S. Pat. No. 5,187,734. Digitized two-dimensional orthographic projections of the component images are formed, high-pass filtered and merged with a digitized, low-pass filtered overview map to form a composite map. Warping, using two-dimensional warping polynomials, is employed to map the component images onto a common set of spatial coordinates on a larger map.
Surveying satellite apparatus that compares sensor measurements with an on-board database to determine misorientation or translation errors is disclosed in U.S. Pat. No. 5,204,818, issued to Landecker et al. The database provides time-dependent upgrades for predicted reference locations, whose locations relative to the satellite change as the satellite moves across a region. The sensor measurements and upgrades can be transmitted to a ground-based user.
In U.S. Pat. No. 5,208,757, issued to Appriou et al, an on-board system for determination of the location of an airborne vessel, such as an aircraft, is disclosed. The spatial coordinates of discrete landmarks on the terrain below are entered into a computer memory. As the vessel flies over a landmark, the known location of this landmark is used to correct the location given by another navigation means that uses images of small portions of the terrain below for location determination. Kalman filtering is applied to the location of the vessel relative to the terrain.
Hong et al, in U.S. Pat. No. 5,208,763, disclose a system for determining location and orientation of a workpiece, using location sensors installed on a machine that handles and processes the workpiece. Location coordinates of selected points on surfaces of the workpiece are measured. A geometric transformation, involving only translations and rotations, is determined, with transformation parameters that are chosen to minimize a mean square error function, depending on the squares of the distances from each selected points to locations of that selected points under the geometric transformation. A similar approach, where the workpiece is an excavator blade used for construction work, is disclosed by Awano et al in U.S. Patent No. 5,363,304.
An interactive automated mapping system that uses location information determined using a GPS is disclosed by Mauney et al in U.S. Pat. No. 5,214,757. Attributes related to location information can be entered, stored and subsequently displayed. The system creates new maps and/or annotates existing maps but does not provide reconciliation between an existing map and a new map.
U.S. Pat. No. 5,271,066, issued to Leonard, discloses apparatus for determining two-dimensional spatial coordinates on a map, using a viewing mechanism that allows scanning and digitization of designated points on the underlying map. An associated scanner can be rotated relative to the underlying map. Another rotatable scanner for capture of image data is disclosed by Faust et al in U.S. Pat. No. 5,280,370.
Interpolation image processing of a digital map is employed to determine pixel color is disclosed in U.S. Pat. No. 5,299,300, issued to Femal et al. Interpolation of pixel color or related data, for a plurality of pixels with spatial locations adjacent to the spatial location of a target pixel, is used to compute to compute the pixel data for the target pixel.
In U.S. Pat. No. 5,321,797, issued to Morton, a system for performing coordinate transformations using stored data is disclosed that interpolates between stored transformed coordinate to determine a suitable transformation for the present location of a user. The quantized and stored location coordinate transformations may be nonlinear functions of selected input variables, such as angles. Input variables are selected by linear interpolation to produce output location coordinates that approximate the user's present location.
Bormans, in U.S. Pat. No. 5,325,482, discloses a system for adding new network data to an existing electronic map, stored in memory. A new map, containing only the new data, is superimposed on the existing map, and corresponding reference points on each map are incrementally moved until they coincide. A third electronic map is then prepared, combining the existing map features with the new data features. Interpolation of reference point locations is sometimes performed.
A system for correcting a compass heading for a vehicle is disclosed in U.S. Pat. No. 5,339,246, issued to Kao. Two or more magnetic compass heading readings are sensed, and a GPS-determined compensation factor is computed to adjust a magnetic heading value to a true heading as indicated by the GPS. The magnetic compass heading and GPS heading values are referenced to a single map.
Wescott et al disclose a polygon-based map display system in U.S. Pat. No. 5,341,463. The system user selects any map center, and a database is used to geometrically describe and display nearby land and water areas as polygons with an arbitrary number of vertices. Calculation of latitude and longitude coordinates for any point on the map are asserted to be determined directly, without requiring any inverse transformations between coordinate systems.
A relative aircraft guidance system using GPS signals is disclosed by Youhannaie in U.S. Pat. No. 5,344,105. First and second airborne vehicles, positioned close together, each carry a GPS antenna and receiver/processor and receives GPS signals from the same group of GPS satellites. Using a selected GPS satellite constellation, the first vehicle locates a target, converts the target location to a reference frame of the selected satellite constellation, and communicates the target location in this reference frame and identity of the selected satellite constellation to the second vehicle, for guidance purposes.
In U.S. Pat. No. 5,345,086, Bertram discloses an automatic map compilation system that extracts three-dimensional surveying or similar information from a plurality of two-dimensional maps. A pair of stereoscopic maps, showing data on terrain and/or associated altitude(s), is scanned into a computer, and altitudes for topographic sections are determined, if desired. An orthographic image projection is prepared from the scanned-in data and may be displayed as a photograph or orthophoto. Three-dimensional coordinates of a point are determined two or more from two-dimensional views.
These patents usually assume that the coordinates for locations of interest in a coordinate system, or in two or more associated coordinate systems, are consistent with each other. Further, the computations and coordinate manipulations are usually performed in a post-processing environment, rather than in a real time environment in the field at the time the survey measurements are made. What is needed is an approach that allows real time processing, preferably at a time contemporaneous with the survey in the field, to optimally determine any adjustments in location coordinates required to reconcile location coordinates for different survey locations with each other. Preferably, two or more approaches for these coordinate adjustments should be available so that a selection of approach can be made a based upon the desired accuracy and/or the particular constraints that are present.